Couple things I've noticed about oval chainrings:
- Smooths out your pedal stroke/cadence when you're not powering down.
- Ratcheting back while climbing technical sections becomes much more effective.
- Reduces the amount of side to side movement on the bike to generate power.
- Not really noticeable after first few pedal strokes.
- Typically ride a 32T circular chainring, but I feel I could go 34T without any issues.
All in all, I was very skeptical at first. It seemed gimmicky. However, it does have it's advantages over circular chainrings. It's not going to make you a climbing pro overnight, but it does help quite a bit.